This paper discusses a phenomenological model used to describe various properties of a dx²−y² superconductor in its temperature as well as frequency dependence, namely, the London penetration depth, the optical conductivity, ...

For a tJ -model in the X -operators representation a generating functional
of the field describing fluctuations of matrix elements of electron hopping
on a lattice is presented. The first order functional derivative with ...

The system of bose liquid + impurity is considered. The energy spectrum,
as well as effective mass of impurity is calculated. For the case of an ³He
atom in superfluid <⁴He numerical calculations are performed.

Strongly correlated electron systems require the development of new theoretical
schemes in order to describe their unusual and unexpected properties.
The usual perturbation schemes are inadequate and new concepts
...

A new diagram technique based on the generalized Wick theorem has
been elaborated for the systems with strong electronic correlations. Coulomb
repulsion of the electrons of the Hubbard model is considered as
the main ...

The concept of generalized collective modes, recently proposed for the
investigation of simple fluids, is now applied to describe processes of dielectric
relaxation in dipolar systems. The approach presented here is ...

Long-wave spin excitations in the perfect s-d model are studied. The Hamiltonian
of the model includes, apart from usually treated spin-electron processes,
the Heisenberg exchange interaction of atomic spins and the ...

We discuss approaches based on the concepts of local electron pairing
and the superconducting properties which they imply. The nature of the
intermediate coupling regime is addressed and a recent progress in the
BCS–Bose ...

Mathisson’s ‘new mechanics’ of a relativistic spinning particle is shown to
follow, in the case of planar motion, from only general requirements of relativistic
invariance and of the dependence on third order derivatives ...

The Lagrangian relativistic direct interaction theory in the various forms
of dynamics is formulated and its connections with the Fokker-type action
theory and with the constrained Hamiltonian mechanics are established.
The ...

A constraint theory is applied to two-particle systems to construct Poincare´
invariant wave equations with interaction potentials. The latter can
be determined in the quantum field theory from Feynman diagrams. ...

Generalization of the Sommers–Sen spinor connection for spinor fields,
associated with the distribution V³₄ is made and on its basis the equations for Weyl and Dirac null vector fields on complexificated V³₄ are ...

The gravitational spin-orbit interaction in the region of the ultrarelativistic
orbital velocity of a spinning test particle in the Schwarzschild field is investigated
on the basis of the Mathisson-Papapetrou equations. ...

Nonlinear effects in screening a high-Z grain immersed in a plasma background
were investigated by means of microscopic Monte-Carlo simulations
and within the Poisson-Boltzmann theory. A distinct difference from
the ...

An attempt to describe the bell-shape dependence of the critical temperature
of high-T<sub>c</sub> superconductors on the charge carrier density is made. It is
proposed to explain its linear increase in the region of ...

A model for the description of materials with narrow energy bands is proposed.
It is shown that in narrow-band materials an electron-hole symmetry
is absent in contrast to the Hubbard model. In this paper a metal-insul ...

A simple electrolyte in a polar solvent is modelled by a mixture of polar hard
spheres and equal diameter charged hard spheres with the possibility of
ionic dimerization. The analytical solution of the associative mean ...

A series of co-authors’ studies [1-7] devoted to the unified model description
of structural phase transitions (SPT) in ferroelectrics and related materials
are reviewed and partly innovated.
Starting from a general ...

We study the effects of hydrostatic pressures on deuterated ND₄D₂PO₄
type antiferroelectric crystals. Within the four-particle cluster approximation
the free energy of the crystals is calculated, and an equation for ...

The theory of the superconductivity mediated by kinematic and exchange
interactions in t−J and two-band Hubbard models in a paramagnetic state
is formulated. The Dyson equations for the matrix Green functions in terms
of ...